The top secret document was retrieved by U.S. whistleblower Edward Snowden. It shows Canada's electronic spy agency used information from the free internet service at a major Canadian airport to track the wireless devices of thousands of ordinary airline passengers for days after they left the terminal.

Under repeated questioning by opposition MPs, Nicholson didn't directly deny the story, but said that the document detailing work by the Communications Security Establishment Canada (CESC) doesn't show that Canadian communications were targeted or used.

"It's my understanding that CSEC made it clear to CBC that nothing in the documents that they had obtained showed that Canadian communications were targeted, collected, or used, nor that travellers' movements were tracked," Nicholson said in the House of Commons.

In fact, the latest Snowden document indicates the spy service was provided with information captured from unsuspecting travellers' wireless devices by the airport's free Wi-Fi system over a two-week period.​ In the case of the airport tracking operation, that information came from metadata that apparently identified travellers' wireless devices, but not the content of calls made or emails sent from them.

Nicholson said that regular reports by a watchdog, the CSEC commissioner, affirm the signals intelligence agency doesn't break the law.

The spy agency is supposed to be collecting primarily foreign intelligence by intercepting overseas phone and internet traffic, and is prohibited by law from targeting Canadians or anyone in Canada without a judicial warrant.

New Democrat MP David Christopherson asked Nicholson to categorically deny the agency has tracked Canadians, but Nicholson returned to his response about the CSEC commissioner.

Nicholson declined to be interviewed by CBC News following question period.

Metadata at issue

Nicholson's argument seemed to hinge on a difference in terminology, referring to communications rather than metadata.

CSEC itself referred to the metadata around a person's communications, which it is legally authorized to collect and analyze as part of its role in gathering foreign intelligence.

"Metadata is technical information used to route communications, and not the contents of a communication," CSEC said in a written statement.

Metadata reveals a trove of information including, for example, the location and telephone numbers of all calls a person makes and receives — but not the content of the call, which would legally be considered a private communication and cannot be intercepted without a warrant.

Charmaine Borg, the NDP's digital issues critic, zeroed in on the question of metadata and their distinction from a person's conversations.

"The seizure of metadata by CSEC concerns Canadians' location, how long their communications last and where they are made, and how they use their data. Is the government really claiming that gathering information is not the same as illegally tracking Canadians?" she said.

Nicholson repeated that nothing in the document "showed that Canadians' communications were targeted, collected or used, nor that travellers' movements were tracked.​"

The document provided to CBC News "is a technical presentation between specialists exploring mathematical models built on everyday scenarios to identify and locate foreign terrorist threats," the agency said.

"The unauthorized disclosure of tradecraft puts our techniques at risk of being less effective when addressing threats to Canada and Canadians. It is important to note that no Canadian or foreign travellers were tracked. No Canadian communications were, or are, targeted, collected or used. And all CSE activities include measures to protect the privacy of Canadians."